1. Field of the Invention
The present invention relates to a plate type integrated optical device using a zigzag optical path, and particularly to an optical device in which an oblique incident angle of a semiconductor laser chip can accurately be set.
2. Description of the Related Art
In an integrated optical device having a plate shape (plate type optical integrated circuit), optical elements are integrated on a transparent plate (substrate), an optical path is formed in a zigzag manner by utilizing reflections between the interfaces of the plate so that the optical elements are connected with each other, and optical information processing is conducted. This circuit configuration has been utilized because it can allow an optical application system to be miniaturized, stabilized, and lightened.
FIGS. 6A and 6B show an example of an optical device using a conventional plate type optical integrated circuit system (Teruhiro Shiono et al., Japanese patent application No. 3-77527).
The optical device shown in FIGS. 6A and 6B, is an example of an optical head for reading out signals from an optical recording device such as a compact disk (CD), an optical disk, or an optical card memory.
In the conventional optical device, light which is obliquely emitted from a semiconductor laser chip 1 disposed on the back face of a transparent substrate 2 travels as propagation light 8 and enters a reflection collimator lens 3' to be reflected and collimated. The collimated light propagates in a zigzag manner, and then is obliquely converged and is output to an optical disk 7 as emitted light 9 by a transmission objective lens 4a disposed on the surface of the transparent substrate 2. Light 10 reflected from the optical disk 7 enters a second transmission objective lens 4b disposed on the surface of the transparent substrate 2, and is collimated to become propagation light 8'. The propagation light 8' propagates in a zigzag manner and enters a reflection twin lens 5' which is a signal detecting element (focus/track error signal detection means) formed on the surface of the transparent substrate 2. The propagation light 8' is split into two parts by the lens 5' and converged into a four-split optical detector 6 disposed on the back face of the transparent substrate 2. The four-split optical detector 6 outputs signals corresponding to the input light. The signals output from the optical detector 6, are a reproduced signal, a focus error signal, and a track error signal, both the focus error signal and the track error signal are positioning signals.
In the conventional optical head shown in FIGS. 6A and 6B, since the semiconductor laser chip is directly disposed on the back face of the substrate, it is difficult to accurately adjust the oblique incident angle. In addition, since the heat sink is realized mainly by a glass substrate, the heat conduction is not good. Therefore, there arises problems in that the output power of the semiconductor laser chip is reduced and that a high power laser cannot be used.
This invention has been conducted in view of these problems, and provides an optical head in which an incident angle of a laser light emitted from a semiconductor laser chip can easily be set, which is free from the reduction of the output power of the semiconductor laser chip, and in which a high power laser can be used.